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Investigation of Interline Dynamic Voltage Restorer with Virtual Impedance Injection

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Journal of Energy and Power Engineering 2012年第1期6卷 101-109页

作者： ahmed elserougi ahmed Hossam-Eldin ahmed Massoud Shehab ahmed Electrical Engineering Department Alexandria University Alexandria 21526 Egypt Electrical and Computer Engineering Department Qatar University Doha 23874 Qatar Electrical and Computer Engineering Department Texas A＆M University at Qatar Doha 23874 Qatar

The inter-line dynamic voltage restorer （IDVR） consists of several voltage source inverters connected to different independent distribution feeders with common dc bus. When one of the inverters compensates for voltage sag that appears in its feeder （voltage control mode）, the other inverters pump the required power into the dc bus （power control mode）. Each inverter will have both voltage and power controllers; only one controller is in use during the abnormal conditions according to its feeder state. The voltage controller uses one of the dynamic voltage restoration techniques. In this paper, the in-phase technique is applied and two types of loads are considered （constant impedance and three phase induction motor）. Since the voltage restoration process may need real power injection into the distribution system, the power controller injects this power via voltage injection. This voltage injection is simulated by voltage drop across series virtual impedance. A new scheme is proposed to select the impedance value. The impedance value is selected such that the power consumed by this impedance represents the required power to be transferred without perturbing the load voltage. The performance of this system is also studied during voltage swell. A scheme for operation of multi-feeder IDVR system is proposed in this paper. Simulation results substantiate the proposed concept.

关键词： Dynamic voltage restorers IDVR voltage sag voltage swell power quality.

Brushless Doubly-Fed Induction Machine as a Variable Frequency Transformer

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Journal of Energy and Power Engineering 2013年第1期7卷 110-117页

作者： Ayman Abdel-Khalik ahmed elserougi ahmed Massoud Shehab ahmed Electrical Engineering Department Alexandria University Alexandria 21544 Egypt Electrical Engineering Department Qatar University Doha 2713 Qatar Electrical and Computer Engineering Department Texas A & M University at Qatar Doha 23874 Qatar

VFT （variable frequency transformer） has been recently used as art alternative to HVDC （high voltage direct current） to control power flow between asynchronous networks. VFT consumes less reactive power than a back-to-back HVDC system, provides faster initial transient recovery, and has better natural damping capability. VFT is simply a DFIM （doubly-fed induction machine） where the machine torque controls the power flow from stator to rotor and vice versa. The main disadvantage of this VFT is the slip rings and brushes required for the rotor circuit, especially in bulk power transmission. The BDFM （brushless doubly-fed machine） with nested cage rotor machine is proved to be a comparable alternative to conventional DFIM in many applications with the advantage that all windings being in the stator frame with fixed output terminals. In this paper, the BDFM is used as a BVFT （brushless variable frequency transformer）. A prototype machine is designed and simulated to verify the system validity.

关键词： Variable frequency transformer brushless doubly-fed machines AC machines induction machine.

Magnetic Gearbox with an Electric Power Output Port and Fixed Speed Ratio for Wind Energy Applications

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Journal of Energy and Power Engineering 2013年第6期7卷 1141-1149页

作者： Ayman Abdel-Khalik Shehab ahmed ahmed Massoud ahmed elserougi Electrical Engineering Department Alexandria University Alexandria 21544 Egypt Electrical and Computer Engineering Department Texas A&M University at Qatar Doha 23874 Qatar Electrical EngineeringDepartment Qatar University Doha 2713 Qatar

Mechanical gearboxes are typically employed with doubly-fed induction generatur-based wind turbines. The main drawback of this solution is the gearbox＇s reliability and maintenance. Using magnetic gearbox in conjunction with the doubly-fed induction generator is an emerging alternative being promoted by the research community which maintains the reduced size doubly-fed machine and overcomes the mechanical gearbox problems reported by field experience. This paper proposes a novel magnetic gearbox configuration in which a conventional planetary magnetic gearbox is equipped with n-phase coils fitted around the ferromagnetic pole-pieces to extract output electrical power. The turbine mechanical power is thus divided into mechanical power to drive the electrical generator and extra electrical power that can be diverted into a storage system to perform the power leveling function. The proposed configuration can also be used to freely modify the power-speed characteristic as seen by the electrical generator, a highly needed feature for grid frequency support.

关键词： Gearbox magnetic planetary gear modular winding permanent magnets wind energy finite elements AC machines.

Flywheel Energy Storage System Based on Boost DC-AC Converter

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Journal of Energy and Power Engineering 2012年第11期6卷 1725-1732页

作者： ahmed elserougi Ayman Abdel-Khalil ahmed Massoud Shehab ahmed Electrical Engineering Department Alexandria University Alexandria 21544 Egypt Electrical Engineering Department Qatar University Doha 2713 Qatar Electrical and Computer Engineering Department Texas A & M University at Qatar Doha 23874 Qatar

To extend the operating speed range of a conventional configuration of FESS （flywheel energy storage system）, an additional DC-DC boost converter is required between the machine and grid side converters to regulate the output voltage. This paper presents a new FESS based on three-phase boost inverter topology. The proposed system facilitates voltage boost capability directly in a single-stage. The main advantage of the three-phase boost inverter is the deployment of only six switches and undersized passive elements to obtain a boosted AC output voltage weighed against the input DC supply. In this paper, FESS based on boost inverter topology is modeled and simulated using MATLAB/S1MULINK. An experimental setup has been built for the three-phase boost inverter to present its boosting capability. The simulation and experimental results sustain the proposed configuration.

关键词： Boost converter flywheel energy storage system FESS.